D3225: A multiyear assessment of abamectin resistance of Tetranychus urticae populations from South-Western Ontario

Abamectin is a macrolytic lactone and belongs to the class of compounds that are either produced by the actinomycete Streptomyces avermitilis or are created through semisynthetic modification. It was first introduced in 1985 as a crop insecticide against mites and some insect species. It is still an important control agent and is frequently used to control two-spotted spider mite Tetranychus urticae. In T. urticae, abamectin primarily targets and binds glutamate-gated chloride channels (GluCl) which causes hyperpolarization of nerve and muscle cells, paralysis, and death. Abamectin resistance was frequently reported in T. urticae populations across the globe. Currently, up to 30% of surveyed populations exhibit some level of abamectin resistance. This resistance was demonstrated to be associated with a number of point mutations in T. urticae GluCl genes (such as G314D in GluCl1, and G326E and I321T in GluCl3), and elevated expression levels of several genes in cytochrome P450 and UDP-glucuronosyltransferase (UGT) families. Here we present a multiyear assessment of abamectin resistance of T. urticae populations coming from South-Western Ontario. Our study covered a variety of crops (cucumber, pepper, soybean, strawberry and tomato), and production systems (greenhouse and field). We also present an attempt to develop a predictive model of abamectin resistance status based on genotyping for known single nucleotide polymorphisms (SNP), and measurement of expression levels of known metabolic resistance markers.